This is first time scientists have been able to use stem cells in a livestock species this way, said Stice and West, researchers in UGA's College of Agricultural and Environmental Sciences.

"This is very significant work for our laboratory, and I think for the world," Stice said Tuesday.

One day, scientists might use a similar method of producing animals with stem cells to help build disease resistance in endangered species or even resurrect extinct species such as the woolly mammoth, West said.

That type of work is far off, the scientists say.

But the discovery might benefit human health much sooner, they said.

"This is an important discovery," said Scott Angle, dean of UGA's College of Agricultural and Environmental Sciences.

The UGA scientists have grown 34 pigs from embryos using the technique - so-called chimeras, because their cells contain more than one set of DNA.

The four 300-pound, mostly white pigs on display Tuesday were about 9 months old - born last Sept. 9 - and looked no different than any other commercial pigs. In fact, the researchers have found no abnormalities in them, West said.

Stice has been trying to perfect the technique for 20 years, he said, but it was finally West who figured out how.

To produce the stem cells, the researchers inserted a sequence of six human genes into pig bone marrow cells, which developed into pluripotent stem cells.

Then, they injected the stem cells into pig embryos, which were then inserted in mother pigs to develop into full-term piglets.

The stem cells were incorporated into the growing embryo and developed into all kinds of tissue types such as muscle, bone and nerve, along with the cells already in the embryos.

Scientists have been able to use a similar technique to produce live mice, but not livestock animals - until now, Stice said.

Mice are not always a good model animal to use in studying human disease.

"Mice do not get clogged arteries," he said.

Mice also are not a good source of tissues and organs, Stice said.

Now, scientists have a way to make pigs that can provide cells and organs for regenerative medicine, the researchers say - creating living, functional tissue to replace diseased or aging organs.

The technique, called induced pluripotent stem cells, avoids the difficult and controversial technique of cloning animals, and makes it easier to alter the new pigs' genetic makeup, the scientists say.

One of the first ways the scientists will use the technology is in a research project with Emory University to find better diabetes therapies.

Researchers hope that pig tissues called islet cells that produce insulin and other hormones can replace similar human islet cells that don't function well in people with Type I diabetes. But human bodies won't accept the cells from pigs.

"The biggest problem they have is rejection," Stice said.

Researchers now will look for genes they could add or remove so that people reject the islets less or not at all, Stice said.

Combined with traditional breeding methods, the technique also could help scientists produce more disease-resistant pigs, Stice said, or pigs that could use feed more efficiently and produce waste that contains less phosphorous, a major water pollutant.